1. Field of the Invention
Exemplary aspects of the present invention generally relate to a security encoding unit and an image reading unit using the same, and an image forming apparatus including the image reading unit.
2. Description of the Background Art
To protect the confidentiality of certain types of information, particularly documents, methods are known of prohibiting unauthorized copying of such documents by inserting various types of encoded security information in the document. Subsequently, when such encoded security information is detected in an attempt to copy the document, copying is either prevented from starting or discontinued if already started.
In particular, Japanese Patent Unexamined Patent Application Publication No. 2004-274092 discloses a method and an apparatus for protecting the security of a document by prohibiting output of an image when a background pattern of a document image is detected.
A background pattern is detected so as to create security encoding instruction information, and a determination as to whether or not a document image is a copy prohibited image is made based on the security encoding instruction information thus created. When a problem is detected by a background pattern recognition unit, an image forming apparatus stops reading the document and also stops forming an image of the document.
Similarly, Japanese Patent Unexamined Patent Application Publication No. 2006-287902 discloses an image processor that prevents unauthorized copying of a document by displaying document property information through not only a background pattern shape embedded in the document but also by a color of the background pattern.
Various refinements of the basic method described above are also known. Thus, for example, Japanese Patent Unexamined Patent Application Publication No. 2006-13882 discloses an image reading apparatus which simultaneously reads images formed on both a front side and a back side of a document, and stores the image data in a memory. Japanese Patent Unexamined Patent Application Publication No. 2002-109527 discloses a multifunction copier in which images formed on both a front side and a back side of a document are simultaneously read, and digitized image data is stored in a memory in a time-division writing scheme using a single channel. Japanese Patent No. 3278471 discloses an area discriminating method (that is, extraction of an image region) which distinguishes between a text region in an image and a non-text region which is not the text region, but may include an image, for example, a picture.
However, the foregoing examples may leave unaddressed certain desired requirements relating to reliable security encoding.
For example, when a plurality of images is simultaneously input, it is desirable that security encoding processing is securely performed on each image. In such a case, when the security information of the plurality of images is detected using the same parameter, there is a possibility that even though the security information of one image is accurately detected, the security information of the other image may not be accurately detected because the input processing characteristics of the plurality of images are different.
Furthermore, it is desirable that the security information of the plurality of images is accurately detected using fewer security information detectors than the number of images to be detected.
Still further, in a case in which one image includes the security information and the other image does not include such security information, it is desirable that the security encoding processing still be performed on the image including no security information as is performed on the image including the security information to provide enhanced security for the information contained in the document.